In a motor-assisted bicycle in the related art, the rotational torque applied to a crankshaft of the bicycle is detected through a non-contact means and the drive force imparted by a motor is used to assist the rider with pedaling. The rotational torque may be detected with, for instance, a magnetostrictive torque sensor having a magnetostrictive detection layer that is rendered magnetically anisotropic, formed at an outer circumferential surface or the like of the crankshaft, and a coil disposed on the outer circumferential side of the magnetostrictive detection layer with a predetermined gap formed between them (see PTL1).
In addition, in a standard torque measuring method known in the related art, torque applied to a rotating shaft is measured via a strain sensor, which measures the torque applied to the rotating shaft by measuring the extent of strain at the rotating shaft with a strain gauge.